Abstract: An optical system with aberration correction is disclosed. The optical system may include an illumination source. The optical system may include a detector. The optical system may include one or more collection optics configured to image a sample onto the detector based on illumination from the illumination source. The optical system may include two or more aberration correction plates located in one or more pupil planes of the one or more collection optics. The two or more aberration correction plates may provide at least partial correction of two or more linearly-independent aberration terms. Any particular one of the two or more aberration correction plates may have a spatially-varying thickness profile providing a selected amount of correction for a single particular aberration term of the two or more linearly-independent aberration terms.

Abstract: In one embodiment, disclosed are apparatus, methods, and targets for determining a phase shift of a photomask having a phase-shift target. An inspection or metrology system is used to direct an incident beam towards the target and then detect a plurality of intensity measurements that are transmitted through the target in response to the incident beam. A phase shift value for the target may then be determined based on the intensity measurements.

Abstract: In one embodiment, disclosed are apparatus, methods, and targets for determining a phase shift of a photomask having a phase-shift target. An inspection or metrology system is used to direct an incident beam towards the target and then detect a plurality of intensity measurements that are transmitted through the target in response to the incident beam. A phase shift value for the target may then be determined based on the intensity measurements.

Abstract: A reticle is inspected with an imaging system to obtain a measured image of a structure on the reticle, and the structure has an unknown critical dimension (CD). Using a model, a calculated image is generated using a design database that describes a pattern used to form the structure on the reticle. The model generates the calculated image based on: optical properties of reticle materials of the structure, a computational model of the imaging system, and an adjustable CD. A norm of a difference between the measured and calculated images is minimized by adjusting the adjustable CD and iteratively repeating the operation of generating a calculated image so as to obtain a final CD for the unknown CD of the structure. Minimizing the norm of the difference is performed simultaneously with respect to the adjustable CD and one or more uncertain parameters of the imaging system.

Abstract: A reticle is inspected with an imaging system to obtain a measured image of a structure on the reticle, and the structure has an unknown critical dimension (CD). Using a model, a calculated image is generated using a design database that describes a pattern used to form the structure on the reticle. The model generates the calculated image based on: optical properties of reticle materials of the structure, a computational model of the imaging system, and an adjustable CD. A norm of a difference between the measured and calculated images is minimized by adjusting the adjustable CD and iteratively repeating the operation of generating a calculated image so as to obtain a final CD for the unknown CD of the structure. Minimizing the norm of the difference is performed simultaneously with respect to the adjustable CD and one or more uncertain parameters of the imaging system.

Abstract: Disclosed are methods and apparatus for detecting a relatively wide dynamic range of intensity values from a beam (e.g., scattered light, reflected light, or secondary electrons) originating from a sample, such as a semiconductor wafer. In other words, the inspection system provides detected output signals having wide dynamic ranges. The detected output signals may then be analyzed to determine whether defects are present on the sample. For example, the intensity values from a target die are compared to the intensity values from a corresponding portion of a reference die, where a significant intensity difference may be defined as a defect. In a specific embodiment, an inspection system for detecting defects on a sample is disclosed. The system includes a beam generator for directing an incident beam towards a sample surface and a detector positioned to detect a detected beam originating from the sample surface in response to the incident beam.

Abstract: Systems and methods for scanning a beam of light over a specimen are provided. A system may include a pre-scan acousto-optical deflector (AOD) configured to deflect a beam of light, a second AOD configured as a traveling lens to focus the scanning beam, a relay lens, and an objective lens. The relay lens may be centered on the scan line produced by the second AOD, while the objective lens may be substantially de-centered with respect to the relay lens to produce a telecentric scanning spot with no field tilt. The system may modulate the amplitude of the sound wave in the first AOD to compensate for attenuation in the second AOD. The system may pre-fill one chirp packet in the second AOD while another chirp packet is scanning to substantially reduce a delay between consecutive scans.

Abstract: Systems and methods for scanning a beam of light over a specimen are provided. A system may include a pre-scan acousto-optical deflector (AOD) configured to deflect a beam of light, a second AOD configured as a traveling lens to focus the scanning beam, a relay lens, and an objective lens. The relay lens may be centered on the scan line produced by the second AOD, while the objective lens may be substantially de-centered with respect to the relay lens to produce a telecentric scanning spot with no field tilt. The system may modulate the amplitude of the sound wave in the first AOD to compensate for attenuation in the second AOD. The system may pre-fill one chirp packet in the second AOD while another chirp packet is scanning to substantially reduce a delay between consecutive scans.